Quantification of the Urban Heat Island Under a Changing Climate over Anatolian Peninsula

18 Pages·2012·1.4 MB·English

by  Intech Prepress

Chapter 5
Quantification of the Urban Heat Island Under
a Changing Climate over Anatolian Peninsula
Tayfun Kindap, Alper Unal, Huseyin Ozdemir, Deniz Bozkurt,
Ufuk Utku Turuncoglu, Goksel Demir, Mete Tayanc and Mehmet Karaca
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/51244
1. Introduction
More than half of the world’s population (i.e. approximately 3.5 billion) has been living in
urban areas in 2010 and by 2030 this number will rise to almost 5 billion (UNFPA, 2011).
In the meantime, global average surface temperature has been increasing significantly:
last century saw an approximately 0.7 °C warming (IPCC, 2007; WMO, 2009). Urban
growth and climate change are two major forcings on local climate (IPCC, 2007).
Urbanization reshapes the surface of the earth causing changes in the energy budget at
the ground surface while altering the surrounding atmospheric circulation characteristics
leading changes in local climate (Huang et al., 2009; Oke et al., 1992). Urban heat island
(UHI) refers to warmer air temperatures observed in urban areas as compared to
those over surrounding non-urban regions. When naturally vegetated areas (e.g., grass
and trees) are replaced with impervious surfaces having relatively low reflectivity
and evapotranspiration rates, additional energy heats the atmosphere causing the
phenomena. After sunset, non-urban areas cool more rapidly than urban regions resulting
in a temperature differential. The UHI is presented as the difference between
temperatures recorded within and outside the urban settlement. It has been suggested
that UHI is influenced by population; topography; level of industrialization as well as the
regional climate (Oke, 1987; Rosenzweig et al., 2005; Gill et al., 2008; Kolokotroni &
Giridharan, 2008).
Anatolian peninsula, (i.e. Asian part of Turkey), is lying in the Eastern Mediterranean, and
has seven distinct geographical regions: Eastern Anatolia; Central Anatolia; Black Sea
Region; Mediterranean Region; Aegean Region; Marmara Region; and Southeastern
Anatolia (Unal et al., 2003; Kindap, 2010). The Aegean and Mediterranean coastal regions
have cool rainy winters, and hot moderately dry summers. Mountains along the coast

© 2012 Kindap et al., licensee InTech. This is an open access chapter distributed under the terms of the
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88 Human and Social Dimensions of Climate Change
prevent the Mediterranean influences from extending inland, giving interior of Anatolian
Peninsula a continental climate and distinct seasons.
As urbanization rate has increased significantly, UHI has become a significant issue in the
Anatolian Peninsula. There have been a few studies focusing on UHI effect over Anatolian
Peninsula (Karaca et al., 1995; Tayanc & Toros, 1997; and Ezber et al., 2007). For example,
Karaca et al. (1995) investigated the effects of urbanization on climates of two cities, Istanbul
and Ankara in the Anatolian Peninsula with varying periods (1912-1992) and reported
significant upward trend for the urban temperatures when compared to the rural
temperatures in the southern part of Istanbul. Tayanc & Toros (1997) studied 4 urban areas
(i.e., Adana, Bursa, Gaziantep, Izmir) suggesting that temperature is more sensitive to UHI
than precipitation and their results showed that the Anatolian Region is under a cooling
trend after the period ending by 1990. Ezber et al. (2007) used statistical and numerical
modeling tools to investigate the climatic effects of urbanization in Istanbul from the period
of 1951 to 2004, and they found statistically positive trends in the urban stations of the city.
These studies focused on cities individually and have not conducted a comprehensive
evaluation of all urban environments in Anatolian Peninsula. The objective of this study,
hence, is to quantify the UHI effect of the all major cities (population>1,000,000) with quality
meteorological data extending back to 1965. Climate forecasts using a regional climate
model output are also analyzed to understand the effect of UHI under a changing climate.
2. Material and methods
2.1. Temperature data
Minimum daily temperature is the primary indicator of UHI (Rosenzweig et al., 2005). We
have, therefore, compiled a database of minimum daily temperatures over urban cities in
Anatolia. As a first step, we have developed and implemented the following criteria: Urban
stations are selected in regions having population over 500,000, and rural stations with
population of less than 100,000 (Hua et al., 2007); high quality temperature data (i.e., passes
homogeneity test, have representative urban and rural stations); continuous data from 1965
to 2006. After comprehensive evaluation, especially for representativeness, we have
identified 8 cities to analyze, a total of 25 meteorological stations (9 urban and 16 rural).
These cities are highlighted in Table 1.
Selected cities have significant increase in urban population between 1935 and 2011,
are shown in Fig. 1. Ratio of the center population is calculated by dividing the center
population (urban districts of the city, not the rural) of the selected cities to the total
population of the city. Dark colored bar in the figure is the ratio of the year 1935, and the
total bar including the shaded and the dark is the ratio in 2011. For example, in 1935
approximately 50% of Istanbul’s population is urbanized, which increased to approximately
to 100% in 2011. In 1935, number of cities that have urban ratio of 50% or more was only one
(i.e. Istanbul), whereas in 2011 all of the selected cities have urban population ratio of more
than 50%.
Quantification of the Urban Heat Island Under a Changing Climate over Anatolian Peninsula 89

100
n Increase till
o 2011
ti
a 80 1935
ul
p
o
P
60
r
e
t
n
Ce 40
f
o
o 20
ti
a
R
0
Selected Large Cities of Turkey

Figure 1. The rate of urbanization in terms of urban over total population (%) in 1935 and 2011

Figure 2. Locations of meteorological monitoring stations
90 Human and Social Dimensions of Climate Change
* Cities highlighted are analyzed in the study
Table 1. Cities with their populations in each climatological region of the Anatolian Peninsula (TUIK, 2012)
Quantification of the Urban Heat Island Under a Changing Climate over Anatolian Peninsula 91
2.2. Study area
Regarded by many as the cradle of civilization of the world, the Anatolian Peninsula is
located at the confluence of Europe, Asia and Africa. This region has 75 million inhabitants
(TUIK, 2012). The population has grown almost 4.7 times between 1935 and 2012, from 16
million to 75 million (TUIK, 2012). Ratio of rural to urban population has changed
dramatically especially after 1980s and urban population ratio reached to about 80% in 2010
(Fig. 3). Table 1 lists the cities in each climate regions with their population. Approximately,
74% of the cities have the population between 100,000 and 1 million; 22% between 1 million
and 5 million. Only 2 cities are below 100,000, and Istanbul is the only megacity (i.e., the city
which has a population of five million or more) in the region having a population of over 13
million. Table 2 gives a classification about the site characteristics of the selected
meteorological stations.

90
Urban population ratio
80
Rural population ratio
70
%
o, 60
ti
ra 50
n
o 40
ti
a
ul 30
p
o 20
P
10
0
1950 1960 1970 1980 1990 2000 2010
Time, year

Figure 3. The population ratio of urban and rural parts of the region over total population from 1950 to
2010 (TUIK, 2012)
92 Human and Social Dimensions of Climate Change
Station Latitude Longitude Altitude (m) Land-use Location and siting
In a residential area at the city center on
Ankara 39° 57’ 32° 53’ 891 Urban
the ground
70 km away from the city center on the
Polatli (Ankara) 39° 35’ 32° 09’ 886 Suburban
ground
Kizilcahamam 50 km away from the city center on the
40° 28’ 32° 39’ 1033 Rural
(Ankara) ground
Beypazari 75 km away from the city center on the
40° 10’ 31° 56’ 682 Rural
(Ankara) ground
Esenboga At the airport in the city center on the
40° 07’ 33° 00’ 959 Urban
(Ankara) ground
Nallihan 120 km away from the city center on the
40° 11’ 31° 22’ 650 Rural
(Ankara) ground
5 km away from the city center at the
Bursa 40° 23’ 29° 01’ 100 Urban
airport on the ground
60 km away from the city center on the
Keles (Bursa) 39° 54’ 29° 13’ 1063 Rural
ground
In a residential area at the city center on
Gaziantep 37° 08’ 37° 37’ 900 Urban
the ground
Islahiye 50 km away from the city center on the
37° 02’ 36° 61’ 706 Rural
(Gaziantep) ground
Istanbul In a residential area at the city center on
40° 97’ 29° 06’ 33 Urban
(Goztepe) the ground
Istanbul In a residential area at the city center on
40° 97’ 28° 79’ 37 Urban
(Florya) the ground
Kirecburnu 25 km away from the city center on the
41° 15’ 29° 05’ 58 Rural
(Istanbul) ground
Kumkoy 30 km away from the city center on the
41° 25’ 29° 04’ 38 Rural
(Istanbul) ground
50 km away from the city center on the
Sile (Istanbul) 41° 17’ 29° 60’ 83 Rural
ground
In a residential area at the city center on
Izmir 38° 39’ 27° 08’ 29 Urban
the ground
75 km away from the city center on the
Dikili (Izmir) 39° 07’ 26° 89’ 3 Rural
ground
In a residential area at the city center on
Kayseri 38° 77’ 35° 49’ 1092 Urban
the ground
40 km away from the city center on the
Develi (Kayseri) 38° 28’ 35° 54’ 1180 Rural
ground
Pinarbasi 75 km away from the city center on the
38° 77’ 36° 61’ 1500 Rural
(Kayseri) ground
Tomarza 35 km away from the city center on the
38° 27’ 35° 48’ 1397 Rural
(Kayseri) ground
In a residential area at the city center on
Mersin 36° 78’ 34° 60’ 3 Urban
the ground
Erdemli Alata 35 km away from the city center on the
36° 38’ 33° 94’ 9 Suburban
(Mersin) ground
In a residential area at the city center on
Sanliurfa 37° 16’ 38° 79’ 547 Urban
the ground
Birecik 65 km away from the city center on the
37° 02’ 37° 96’ 345 Rural
(Sanliurfa) ground
Table 2. Site characteristics of selected meteorological stations
Quantification of the Urban Heat Island Under a Changing Climate over Anatolian Peninsula 93
2.3. Urban Heat Island
The UHI effect refers to an increase in urban air temperatures as compared to surrounding
suburban and rural temperatures (Oke, 1982; Quattrochi et al., 2000).
UHI effect is defined as:
T  T  T (1)
ur u r
where T is the urban station temperature, T is the rural station temperature, T r is
u r u
the effect of UHI.
Heat islands develop in areas that contain a high percentage of non-reflective, water-
resistant surfaces and a low percentage of vegetated and moisture-trapping surfaces
(Rosenzweig et al., 2005). In particular, materials such as stone, concrete, and asphalt tend to
trap heat at the surface (Landsberg, 1981; Oke, 1982; Quattrochi et al., 2000) and a lack of
vegetation reduces heat lost due to evapotranspiration (Lougeay et al., 1996). The addition
of anthropogenic heat and pollutants into the urban atmosphere further contributes to the
intensity of the UHI effect (Taha, 1997). The pollution created by emissions from power
generation increases absorption of radiation in the boundary layer (Oke, 1982) and
contributes to the creation of inversion layers. Inversion layers prevent rising air from
cooling at the normal rate in urban areas.
Globally average surface warming is projected to increase for the end of the 21st century
(2090 to 2099), relative to 1980 to 1999 within the six different scenarios between 1.1 - 6.4 C
(IPCC, 2007). Climate change has the potential to significantly alter the intensity and
increase the spatial extent of heat islands in urban environments. As temperature warms,
the frequency with which UHI conditions occur could grow (Rosenzweig et al., 2005).
2.4. Mann-Kendall trend test
Trend analysis can be used to assess the climatic variations of the atmosphere and the
Mann-Kendall trend test (Mann, 1945; Kendall, 1975) is one of the widely used non-
parametric tests to detect significant trends in time series. The Mann-Kendall trend test is
not affected by the actual distribution of the data and is less sensitive to outliers rather than
parametric trend tests, which are more powerful, but more sensitive to outliers. Therefore,
Mann-Kendall test is more suitable for detecting trends in temperature time series, which
may have outliers (Hamed, 2008). Climate change can be detected by the Kendall coefficient
t (Mann test) and when a time series shows a significant trend, the period from which the
trend is demonstrated can be obtained effectively by this test. In a time series, for each
element yi, the number ni of elements yj preceding it (i > j) is calculated such that yi > yj.
The test statistic t is then given by,
tn, (2)
i
94 Human and Social Dimensions of Climate Change
and is distributed very nearly as a Gaussian normal distribution with an expected value of
E(t) = n(n-1)/4 and a variance of vart = n(n-1)(2n+5)/72. A trend can be seen for high values of
│ │
u(t) , where,
tE(t)
u(t) , (3)
vart
This principle can be usefully extended to the backward series and u u(t) can be
i i
obtained. The intersection of the u(t) and u’(t) curves denotes approximately the beginning
of the trend. This is called the sequential version of the Mann-Kendall test (Goossens &
Berger, 1986). If a Mann-Kendall statistic of a time series is higher than 1.96, there is a 95%
significant increase in that particular time series. If the result is just the reverse; lower than -
1.96, there is a 95% significantly decreasing trend in the series. Also, results between 0.5 and
1.96 indicate increasing, -0.5 and -1.96 indicate decreasing trends, and 0.5 and -0.5 indicate
no trend. The Mann-Kendall statistics are then plotted on a map in order to show the spatial
distribution of both the significant and non-significant temperature trends in Turkey.
3. Results and discussion
Observation data over the Anatolian Peninsula were analyzed to understand trends in
average temperature. As can be seen in Fig. 4a, as of 2009, average temperatures in all 8
cities are higher than temperature in 1960s. For example, average temperature increase in
Kayseri, Gaziantep, and Mersin is over 2 C. Fig. 4b presents anomaly in mean temperatures
in Anatolian Peninsula as estimated using gridded dataset obtained by the Climate Research
Unit (CRU - TS3.0). The results suggest an increase of 0.5 C starting in 1990s.
Trends in daily minimum temperatures at individual meteorological stations were
investigated with the Mann-Kendall trend test (Mann, 1945; Kendall, 1975). As an example,
annual time series of minimum temperatures for the urban stations of Istanbul (Goztepe &
Florya) and its sequential version of the Mann-Kendall test graph is presented in Fig. 5. In
Mann-Kendall plots, as of 1965, Goztepe station has a minimum temperature of 10 °C,
which increased to 11.5 °C in 2006. Similar trend is seen for Florya station. Significance of
the trend has been identified by Mann-Kendall statistics where the area above the line
passing 1.96 represents the 95% significance level. Both Goztepe and Florya stations show a
significant increase starting by mid to late 1990s.
The Mann-Kendall statistic of the annual minimum temperatures for the urban and rural
stations are presented in Table 3. In all urban stations, Mann-Kendall statistics suggest
statistically significant increase. In rural stations, however, out of 16 stations, 13 stations do
not show any significant trend; only 1 of them have statistically significant increase and 2 of
them show decreasing trend. After 1990s, the population of Beypazari and Tomarza are on
the decline, and this may be the reason for the negative trends in these two rural stations.
These results suggest that an additional factor: possibly UHI, is in motion to cause
significant increase in minimum temperatures over urban areas. In order to further
Quantification of the Urban Heat Island Under a Changing Climate over Anatolian Peninsula 95
investigate this hypothesis, we have studied trends in temperature differences between
urban and rural environment for the selected cities.

(a)
(b)

Figure 4. (a) Observation mean temperature variation in large Anatolian Cities and (b) anomaly in
yearly mean temperatures in the Anatolian Peninsula from 1965 to 2006
96 Human and Social Dimensions of Climate Change
(a)
(b)

Figure 5. The annual time series of minimum temperature for the urban stations of Istanbul and its
sequential version of the Mann-Kendall test; a) Goztepe, b) Florya

Urban Station Tmin Statistics (1965-2006)
Ankara* 2,93
Bursa* 2,20
Gaziantep* 4,87
4,19
Istanbul (Goztepe)*

Istanbul (Florya)* 3,46
Izmir* 2,61
Kayseri* 5,08
Mersin* 7,06
Sanliurfa* 4,35
(a)